The equation x2 + (y + 4)2 = 49 models the boundary on a local map for which Darren can hear his friend Tom on

The equation x2 + (y + 4)2 = 49 models the boundary on a local map for which Darren can hear his friend Tom on his two-way radio when Darren is at home. How far (in miles) can Tom walk from Darren's home and still be heard?

3.5 miles

4 miles

14 miles

7 miles

It's 7 miles. Just look at the more simplified version of the equation: x^2+y^2 = 49. It can be heard at 0,7 0,-7 7,0 -7,0

Doug, that point is still 7 miles from Darren's house, the difference is from 0,-4 to 0,-11, which is still 7 miles.

Actually, I was assuming Darren's house was at 0,-4, Doug was assuming it was the origin. That should have been given in the question.
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I actually think the answer is 11 miles. This would be the case where Tom walks 11 miles due south of Tom's house.

x^2 + (y + 4)^2 = 49
0^2 + (-11 + 4)^2 = 49
0 + 49 = 49
49